The present invention relates to a locking and releasing device for use with a panel plate. More particularly, the invention relates to a device that is attached to the two corners of one side of a panel plate for assisting its insertion into or removal from a housing or rack. The panel plate inserted is securely fixed in the housing along the channels or ducts in the open end of the housing. The device may also be used to release the inserted panel from the open end of said housing.
1. Field of the Invention
The panel plate, also called a panel board, is a rigid card-like structure. An electric circuit is printed on one or both sides of the plate and electronic parts such as resistors, capacitors and semiconductor devices are mounted on said circuit. The panel plate is a member of an electronic apparatus and has printed thereon a program necessary for the operation of said apparatus. A plurality of such panel plates are arranged parallel and closely spaced in a housing or rack. The bottom or rear end of the housing or rack is provided with receptacles for electronic terminals composed of a plurality of lines for connection to the electronic circuit. Each of these receptacles mates with those terminals, either fixed or unfixed, of the printed circuit which are provided at the underside or rear end of the card-like panel plate. The inner side of each of the two opposing walls of the housing is provided with parallel grooves, and the panel plate is nested in the housing by being fitted into the two opposing parallel grooves. The spacing between adjacent parallel grooves is small, and in order to ensure tight, rather than loose, fitting of the panel plate, frictional holding forces are provided between the inner wall of the groove and the plate. Therefore, a considerable force must be applied to insert the plate into the housing or to extract it from the latter. Furthermore, when a plate is withdrawn from the housing against the frictional holding force, great care must be taken to prevent damage to the adjacent plate. As already mentioned, panel plates nested in the housing are arranged at small spacings, so a new plate must be inserted by pushing one end of the plate toward the bottom or rear end of the housing. When removing one plate, both ends must be pulled up by hands. Before pulling up a panel from the housing, the terminals at the underside or rear end of the plate are disengaged from the receptacle for electronic terminals. Then, the plate is pulled up from the housing. In this procedure, a force is necessary for both disengaging the fitting between the plate and receptacle, and for sliding the plate along the grooves outwardly. This force is relatively strong and provided by holding each corner of one side of the plate by the thumb and the forefinger. Initially, the plate will not slide easily, so a greater force must be applied by the two fingers, and this force sometimes urges the plate surface in such a manner that the plate sliding along the grooves deviates from the groove interior. If this occurs, the plate being withdrawn twists and as a result, the surface of that plate or components on this surface may damage the adjacent plate. Therefore, it involves great difficulty in withdrawing panel plates from the housing.
2. Description of the Prior Art
Conventionally, part of this difficulty is eliminated by a releasing device comprising a riding saddle body with two parallel leg plates, which are slipped over both ends of the top of a panel plate and a pin is inserted through apertures in the leg plates so that the saddle body is pivotally mounted on both ends. An example of this releasing device is shown in U.S. Pat. No. 4,261,076. The device shown in this prior patent is a unitary body comprised of relatively rigid parallel leg plate-like complementary halves interconnected along their common edges by a flexible hinge, one of the parallel leg plate-like portions carrying a pin extending therefrom which mates with an aperture in the opposing complementary half. This device is so designed that when the complementary halves are folded together along the flexible hinge, the pin is forced into the aperture in the opposing complementary half. The process of inserting a plate into the housing proceeds as follows. First, the pin on the unitary body is forced into each of the apertures made in both corners of top side of the plate. Then, one of the opposing complementary halves is folded about the edge of the plate until the pin is forced into the aperture in the other complementary half so as to secure the unitary body on the plate in a pivotable fashion. The inserted plate can be extracted from the housing by the following procedure. First, each of the saddle bodies is pivoted around the pin until that portion of each parallel leg plate which extends beyond the pin contacts the top face of the housing. The resulting force of reaction pushes down the top face of the housing and permits the top side of the panel plate to rise above the housing. Then, the panel plate can be extracted from the housing by lifting its top side with one or both hands. However, if the panel plate being withdrawn twists even slightly, it urges the inner surface of one or both of the complementary halves. If the force of this urging is strong, the complementary halves come apart and the pin slips out of the aperture in one complementary half. As a result, the proper relationship between the panel plate and unitary body is lost, and the unitary member may be disengaged from the plate to destroy the flexible hinge.
Another conventional releasing device is also a riding saddle body having a pair of parallel leg plates that extend in the same direction from the saddle seat and which are spaced apart by a distance substantially equal to the thickness of the panel plate. The portions of the leg plates farther from the saddle seat are provided with a pair of apertures in alignment with each other. As in the first example of the conventional device, this saddle body is fitted over both corners of the front edge of the panel plate in such a manner that the centers of the apertures in the leg plates are aligned with the center of the aperture in the corner of the plate. Before use, a pin is thrusted into these apertures. The manner of using this second conventional type of releasing device is substantially the same as the already shown first type in the form of a unitary body. However, the pin used with the second type of the releasing device is generally smaller both in diameter and length and is liable to become off-centered with the apertures bored in the panel plate and the leg plates of the saddle body. If this loss of axial centering occurs, the pin cannot be hammered into the apertures without bending or breaking. Therefore, great care must be exercised to achieve the complete axial centering between the pin and apertures, and this results in a prolonged saddle mounting operation.